<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>标题</title>
    <style type="text/css">
    div {
        width: 100px;
        height: 100px;
        margin: 20px;
        background: red;
    }
    #sss{background: green}
        .zzz{background: purple }
    </style>
</head>
<body>
    <div class="zzz"></div>
    <div id="sss"></div>
    <div id="zzz"></div>
</body>
</html>